Cuomo in January proposed his spending proposal for the 2014-15 fiscal year, which included an estimated $2 billion surplus by the 2016-17 fiscal year if the state limits its spending increases to 2 percent each year.

But Comptroller Thomas DiNapoli on Monday said Cuomo's plan doesn't include "specific proposals" for how the state can achieve that goal. In a report, DiNapoli's office questioned how the state would stay within its spending goal when increases in Medicaid and education costs are expected to exceed it.

In a statement, DiNapoli said the state is in "its strongest fiscal position in years," and Cuomo and lawmakers "deserve credit for putting us on the right path." But Cuomo's projected surplus remains up in the air, he said.

"Still, without specific proposals on how spending will be limited to 2 percent in the coming years, it remains to be seen how the state will stay on track and how future surpluses can be achieved, especially if the pace of economic recovery slows," DiNapoli said.

As part of his budget, Cuomo proposed a tax-cut package of more than $2 billion which relies, in part, on developing a surplus. Cuomo and lawmakers have held to a 2 percent limit on state spending increases since he took office in 2011, but there is no law requiring they do so.

In his report, DiNapoli's office said the state currently projects a $310 million surplus for the current fiscal year. If Cuomo's 2 percent spending limit is ignored, the budget anticipates a $1.5 billion budget gap in 2015-16, a $2.2 billion gap in 2016-17 and a $3.4 billion shortfall in 2017-18.

In Buffalo on Monday, Cuomo hailed the state's fiscal discipline. He said the state has kept the rate of spending to 0.9 percent since he took office in 2011, far below any of his recent predecessors. And he said the state has cut income taxes.

"This budget recognizes that when you cut taxes, you actually stimulate the private-sector economy," Cuomo said.